Reciprocating action liquid pumps and in particular in fuel injection pumps



June 14, 1960 P. E. BESSIERE 2,940,398

RECIPROCATING ACTION LIQUID PUMPS AND IN PARTICULAR IN FUEL INJECTION PUMPS Filed Dec. 3, 1957 3 Sheets-Sheet 1 //\/VENTOR 'MERRE ETKENNE BESSERE 1o ziggk hum+mum ATTORNEYS June 14, 1960 P. E. BESSIERE 2,940,398

RECIPROCATING ACTION LIQUID PUMPS AND IN PARTICULAR IN FUEL INJECTION PUMPS Filed Dec. 3, 1957 3 Sheets-Sheet 2 INVENTOR 'PVEKRE EHENNE ZBES'SUERE ATTORNEYS June 14, 1960 P. E. BESSIERE RECIPROCATING ACTION LIQUID PUMPS AND IN PARTICULAR IN FUEL INJECTION PUMPS S Sheets-Sheet 3 Filed Dec. 3, 1957 /NVENTOR PIERRE FUENNE BESSWRE BY M PLM'YW ATTORNEYS Sr United States Patent RECIPROCATING ACTION LIQUID PU'MPS AND IN PARTICULAR 1N FUEL INJECTION PUlVflS Pierre Etienne Bessiere, 55 Blvd. du Comandant Chafcot, Neuilly-sur-Seine, France Filed Dec. 3, 1957, Ser. No. 700,376

Claims priority, application France Dec. 6, 1956 Claims. (Cl. 103-41) The present invention relates to reciprocating action pumps, that is to say pumps in which the driven part (piston, diaphragm or the like) has a reciprocating movement in a fixed part to produce a chamber of varying volume for suction and delivery of the liquid. My invention is more especially but not exclusively concerned with pumps of this kind for the injection of fuel into internal combustion engines.

The chief object of my invention is to provide a pump of this kind which is better adapted to meet the requirements of practice and in particular which achieves an automatic regulation of its delivery as a function of the speed at which it is driven.

The pumps with which my invention is concerned include a reciprocating member, preferably in the form of an auxiliary piston movable in an auxiliary cylinder rigid with the fixed part of the pump, for instance the cylinder thereof which will be hereinafter called main cylinder, said auxiliary cylinder being divided by said auxiliary piston into two chambers, to wit afirst chamber connected with the main cylinder and a second chamber connected with the delivery conduit of the pump, with an outwardly opening check valve between said second chamber and said delivery conduit, said auxiliary piston being moved in one direction by the liquid delivered into said first chamber by the delivery strokes of the main piston of the pump, against the action of resilient means urging said auxiliary piston in the opposed direction.

According to my invention, said two above mentioned chambers are connected together, at least for some positions of said auxiliary piston, by a by-pass conduit, and a discharge conduit, starting from an intermediate point of the wall of the auxiliary cylinder so as to communicate with said first chamber when the auxiliary pistonhas moved a given distance in the first mentioned direction, is provided with means for throttling it, whereas the auxiliary piston controls means for placing a second discharge conduit in communication with the second chamber at the same time as the first discharge conduit is placed in communication with the first chamber, the orifice of said by-pass conduit into said second chamber being so located as to be closed when said two discharge conduits are, in communication with said chambers respectively.

Preferred embodiments of my invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example, and in which:

Fig. 1 is an axial sectional view of a fuel injection pump made according to a first embodiment of my invention.

Fig. 2 is a similar view of another embodiment of my invention.

Fig. 3 is an axial sectional view showinga modification of the means for throttling the first mentioned. discharge conduit. 7

The pump shown by the drawings includes a main cylinder 1 cooperating with a main piston 2 driven through any suitable means such for instance as a cam; (not 3, this opening 3 being-cleared when piston 2 is in its lower dead center position as shown by the drawings.

' The main cylinder 1 communicates, through a conduit 5 provided with a check valve 6, with the lower chamber 7a of an auxiliary cylinder 7 containing an auxiliary piston 8 which divides this cylinder 7 into two chambers 7a and 7b. A return spring 9 is interposed between the top end of cylinder 7 and auxiliary piston 8, this spring being preferably adjustable by means of a screw 10. Spring 9. urges piston 8 toward the position of rest thereof in which it is applied against a shoulder 11 provided at thelower end of cylinder 7.

A fuel delivery conduit 12 starts from the chamber 7b of, cylinder 7, advantageously at a point of they cylindrical wall of said, chamber located near the upper end thereof. Delivery conduit 12 is provided with a check valve- 13 and leads to the injector o'r injectors to be fed with fuel by the pump.

Chamber 7a is connected with chamber 7b through a by-pass conduit 14 which is opened at least for some positions of auxiliary piston 8, said by-pass conduit being controlled by a slide valve 15 which closes it during the delivery (upward) stroke of main piston 2 and which opens it during the suction (downward) stroke of this piston and possibly during the time piston 2 remains stationary in its lower dead center position (as shown by the drawings). Slide valve 15 is movable in a cylinder 16 one of the ends of'which communicates through a conduit 17 with the top of main cylinder 1. The other end of cylinder 16 contains a spring 18 weaker than the return spring 19 of check valve 6. This spring 18 urges slide valve 15 toward therposition in which it is applied against a shoulder 20, by-pass' conduit 14 being their cleared due to the fact that a groove or a recess of said slide valve 15coincid'es with said conduit 14. The final 7 position occupied by slide valve 15, when it is pushed by the pressure of the liquid supplied through conduit 17 is determined by an abutment 22 hearing against the top end of cylinder 16'.

By-pass conduit 14 may open into chamber 7d either below shoulder 11 or immediately above it. In this last case, auxiliary piston 8 in its position of rest closes the opening of conduit 14 into chamber 7d. I

A discharge conduit 23 starts from a point of the of cylinder 7 located at a distance a above shoulder 11. Thus, the liquid in chamber 7a is' discharged to the out- 1 side when auxiliary pis'to'n 8 has moved upwardly in cylinder 7 a distance sufiicient to clear the orifice 23a of discharge conduit 23.

According to the main feature of my invention, said discharge conduit 23 is throttled at 24 by means ofa throttling member 25 preferably adjustable and constituted for instance by a screw; Furthermore, auxiliary piston. 8, as soon as it clears dischargeconduit 23, closes the orifice 14a of conduit 14, while making it possible for the liquid present in chamber 7b to be discharged to 1 the outside. For this'purpose, the opening 1400f conduit shown); a fuel feed conduitflopens into acylinder'l at 14-islocated at a distance above the top of piston 8 equal to a when said piston is applied against shoudler 11.; And, to permit discharge of-the liquid from chamber when orifice 23a is clearedand orifice 14a is closed, I provide in. auxiliary piston 8 a conduit 26' one of the ends of which opensinto the top end-face of said piston 8. and theother endof-which opensat 26a'int'o the cylin drical Wall. ofsaid piston, so as to be ableto' cooperate with a discharge conduit 27 providedin cylinde'r'7. con: duit 27 isv provided with a check'valve' 27a. Said dis? charge conduit opens into cylinder 7 through a longitudinal groove-28, thelower end of which'is located-at a distance a above the opening 26a of conduit 26 when auxiliary piston 8' is appliedi against shoulder 11. Thus, oncediquidi has be'g'uri to be discharged through conduit" A speed ofpistonz 2 7, the communication maintained between said conduit 27 and the conduit 26 provided in piston 8.

The operation of such a pump is as follows:

When the main pump piston 2 starts moving upwardly.

a it would remain stationary in this position, I q excess of i a fuel delivered by piston 2 (which is then still moving up: wardly) flowin'g out through conduit 23." Then, at the beginning of the downward movement of piston 2, slide valve 15 :being pushed back againstshoulder 20 and thus 7 p n a -Pas 4 -.a x liary .p s o would ately 'opsu 234 a wu d..move ow in y der 7, driving the fuel present in chamber 7a. through bypass conduit 14 into chamber'jb after which, during the next upward stroke of piston land therefore of auxpiston8, fuel present in chamber-1b would be deliveredby said pistonfi into delivery conduit 12.. No

automatic regulation of the. delivery would be obtained inthese conditions, v

Q The operation is much different when discharge conduit 23 is provided with throttling means such as 24. In this case, the upward movement of'auxiliary piston 8 is not stopped assoon as said piston has cleared the orifice 23a of conduit 23; as said pistonS keeps movingupwardly beyondthisposition, it causes the liquid present in chamber 71; to be discharged through conduit 26 and -27,,t he orifice.14 a of by-pass conduit 14 being then closed. The height to which auxiliary piston8 will thus move upwardly depends upon the speed at which the piston; of the pump is being driven, that is to say upon thespeediof, the engine supplied withfuel by the injection pump. This is duev to the fact. that the. presence of throttling means at, 24 in discharge conduit 23 maintains a pressure in chamber 7a practically until piston 2 has Isached the ,topof its upward movement, .whereas the pressure'in chamber 7b is the atmospheric pressure due tothecooperation of conduits 26 and '27.

' It'is known that the presence ofthrottling means in a spending to a displacement a through bypass conduit 14 into chamber" 7b. This amountof fuel must first fill up the vacuum formed above piston 8 in chamber 7b, the importance of this vacuum depending upon the length of the movements of piston 8 beyond the position thereof in which it cleared the orifice of dischargeconduit 23 and it is only the differencebetween the piston dsiplacement corresponding to distance i: and the volume corresponding to this vacuum tha'tis truly delivered through delivery conduit. 12utoward the injector or injectors.

It follows that this amount of fuel is the smaller as the speed of piston 2 is higher (and piston 8 has moved higher p in cylinder 7).

The delivery rate of the pump is therefore automatically regulated inaccordance with the speed of piston 2.

Furthermore, for speeds of the pump above a value corresponding to the limit speed of'the engine (i.e.' the speed which. must not be exceeded by the engine) the pump ceases to deliver fuel. This is due to the fact that when piston 18 movesdown from .its "highest position to the position where it closes orifice 23a and opens orifice 14a, the speed of said auxiliary piston is braked by the provision of throttling means at 24. If, due to an increase of the speed of piston T2, the time taken by-the auxiliary piston to move through said first portion of its downward strokebecomes equal to the time elapsing between the beginning of the suction (downward) stroke of piston '2. and the beginning of its next delivery (upward) stroke,'the fresh stream of fuel. delivered by pisconduit creates a pressure drop which is proportional to V a'powerigreaterthan 1 ofthe speed. Theratio f speed of auxiliary piston 8;

therefore increases constantly during the upward stroke of piston 2 when the speed of said piston increases and the distance travelled over bypiston'8 therefore increases for a given stroke of pistonz when the speed of this piston increases. Consequently the height of'which piston- 8 will move above'opening 23a will be the greater as the speed of pistonZ is higher.

ton z'prevents auxiliary piston Q from effecting the second portion of its downward stroke. Now, this second portion of the downward stroke of piston Sisthat during which it moves, after closing opening 23 a,- onto shoulder .11. Thereforethe auxiliary piston starts back on its next upward stroke'without having been able to deliver fuel through by-pass conduit 14 to chamber 7b The pump shown by Fig. 1, even if it includes only the elements which have been above described, ensures an automaticregulation of the delivery and also a limit speed beyond whichthere is no delivery of fuel;

In order furtherto improve the automatic regulation effect, it is advantageous to vary the lengthlof'the second portion ofthe downward stroke of auxiliary piston 8 as a function of the speed of the-pump piston 2. 'This result may be obtained 'by'making use of the so-called liquid abutment phenomenon described in my US. patent application Ser. No. 673,343 for .Improvements in reciprocating liquid pumps, and in particular in fuel injection pumps. V

--For this purpose, I provide means for. throttling bypass conduit 14*at 29,'such means being for instance constituted byja' screw '30. With this arrangement the down- During its upward-'moivementabove'the level of orifice 23a, auxiliary *piston' 7 discharges into the fuel tank through conduits 26 and 27 an amount of fuel proportionalto the height reached above said opening 23a.

When the auxiliary piston moves down 'as a result of the downward movement of piston 2, the auxiliary piston first creates a corresponding vacuum in chamber 7b. Furthermore,- during its downward movement, auxiliary piston 8 discharges the liquid present in chamber 7a through discharge conduit 23' until the opening 23a of this conduitjs closed and the opening 14a-of by-pass conduit 14- is opened. If thespeed of piston. 2Z(and.conseq1.ientlyv that 'ofgthe engine'supplied with fuel by the pump) is lower than a limit speed which'willbe hereinafter re ferred to, the auxiliary piston, after it has closed opening 23a and opened opening 14a, drops suddenly onto shoulder d1 while deliveringan amount of fuel corre conduit 14 at 29canno longer reach shoulder 11. i

The increase'of'the vacuum in chamber 7b when the speed of the piston pump increases is therefore accompanied by a reductionof the amount of fuel delivered by the auxiliarypiston into said chamber 7b. A particularly efficient self. regulation is vthus obtained.

Fineness of this self regulation is determined by the following factors: a a a If t is the time taken bythe'auxiliary piston to move down from its highest position to the position in which it closes opening 23a and opens opening 14a and if t, is .the time elapsing between the passage of the auxiliary piston'in the last mentioned position and the stopping thereof by theliquid abutmentfl obtain for the total ment just starts being formed, time t is for instanceequal to 4t the limit speed is reached when T passes from the value it had just when the liquid abutment starts being formed to the value T-i-l/ST. Therefore injec tion will be wholly stopped for a variation ofithe speed equal to As a matter of fact, limitation ofy/the speed takes place before injection is WhOllY stopped be-', cause injection of a minimum amount of fuel iSJnecessary to overcome the friction forces created in the engine. Therefore, the finenessof regulation will be smaller than 20%, being for instance equal or even lower than 15%. and this regulation will be an all speeds regulation. It is possible to adjust the fineness of regulation at a me, determined value even when the engine is running by varying either the cross section at the throttled portion of theconduit. or the force of spring 9. In order to obtain a constant fineness, the simplest way is to act upon screw it) in order to vary the force of spring 9 instead of moving the throttling screws 25. and the adjustment oflwhich mustthen be inter-related, which is more gdifiicult to obtain.

In the construction illustrated by' Fig. l, the same throttled passage 24 serves both to create the pressure in, chamber 70; which causesauxiliary piston 8 to move above the position in which it clears orifice 23a and to brake the how of fuel discharged by said piston 8' when itmoves down toward the position in which it closes orifice 23a, However, in some cases it is preferable to provide different throttled passages acting respectively during the upward movement of piston 8 and during its downward movement. For this purpose, I might of course provide means operative in accordance with the movements of the auxiliary piston 8 to act upon an element the posi tion of which determines the cross section ofthe throttlfed passage.

However, it seemsv more advantageous to use the. arrangement illustrated by Fig. 2 according to which discharge conduit 23 is divided into. two branches 31 and 32 each of which is throttled at 33 and 34 respectively, preferably in an adjustable manner, for instance 'by means of screws 35 and 36 respectively. These two branches 31 and 32 of the discharge. conduit are controlled by slide valve 37 movable in a cylinder 38, under the action, in one direction of the pressure existingin the main pump cylinder 1 when its piston 2 is moving upwardly and, in the other direction of a return spring 39. Thus, the lower end of cylinder 38 is connected by a conduit 40 with the top of cylinder 1. Slide valve 37 isprovided with two grooves 41 and 42 positioned insuch manner that, in one of the positions of the slide valve, which is given thereto when piston 2 is moving upwardly, branch 31 is opened and branch 32 is closed, whereas in the other position of slide valve 37' (as shown by the drawings) branch 32 is opened and branch 31 is closed.

According to a modification which is not shown by the drawings, the two slide valves 37 and 15. might be combined into a single one.

The pump shown by Fig. 2 further includes a conduit 48 one of the ends of which is connected with by-pass conduit 14 at a point thereof located between slide, valve 15 and the throttled passage 29, the other end ofsaid conduit 48 opening into cylinder 7 at "a point 481: located above orifice 14a. This conduit 48 may be either opened or closed by means of a needle valve 49 which may also serve to throttle it more or less. During normal operation of the pump, conduit 48 is closed by needle valve 49. On the contrary, when conduit 48 is opened, it permits period, an increased fuel delivery. the volume of which may-be at-most equal to that of a cylinder having the samefdiameter as cylinder 7 and of a height equal to the-distance between the level of orifice 14a and that of orifice 4812.

Of course, instead of using such a conduit 48, I may apply to the pump according to my invention other equivalent arrangements such as that described in my above mentioned prior patent application.

According to'another embodiment of the invention, to improve the self regulation effect, some throttled portions of the conduit instead of being fixed although adjustable (see Figs. 1 and 2.) undergo a modification of their cross section in order-to'produce a variation of the pressure drop. For this purpose, and concerning the discharge branchconduits 3'1 and 32, it seems particularly advantageous; to make use of-a delayed movement of slide valve 37 in order to produce a gradual closing of the conduits controlled by said slide valve.

In the modification illustrated by Fig. 3, this gradual closing achieved bysaid valve 37 is applied only to branch conduit 31 so that this branch conduit does-not require the provision of throttling means such as shown at 33 on Fig. 2; But branch conduit 32keeps the fixed but adjustable means 36 for throttling it at 34.

- In order to obtain a gradual closing of branch conduit 31 by the mutual action of the cooperating surfaces of this branch conduit and of the groove 31 of said valve 37, I providethis slide valve with a rod 43 adapted to come into contact with a cap 44-applied'by a spring 45 against a shoulder ,46 after slide valve 37 hasmoved under the action of the fuel compressed in pump cylinder -1 a distance b-l-d (d being equal to theheight of branch conduit 31) just sufiicient to bring the upper-wall of groove 41 to the level of the upper wall of conduit 31 so'that said conduit is then wholly opened. When slide valve-37 is moved upwardly beyond this position, the passage is more and more throttled as a function, on the one hand of the pressure existing in cylinder 1 and conduit 49 and, on the other hand oi the compression of spring 45.

Ifthe cooperating'portions of groove 41 and conduit 31 are suitably chosen, it is possible to obtain any desired values for the variations of the pressure drop due tothe throttling of the passage. Thus, the pressure drop may increase asa power of the speed greater than the second power. It is for instance easy to reachthe fourth power.

- Insteadof braking the upward movement of slide valve 37 by means of a spring'such as 45 the force of which maybe adjusted by means of a screw 37, I may use a liquid which'wouldbe discharged by cap 44, acting as a piston, through a restricted passage.

The present invention may be applied to pumps of the kind illustrated by Figs. 5 to 7 of my above mentioned prior application, where the upward movement of the auxiliary piston does not serve to drive into the delivery conduit the fuel that has been metered by the auxiliary piston but the movement of said piston serves merely for self regulation and speed limiting purposes.

What I claim is:

1. A reciprocating action liquid pump which comprises, in combination, means forming a variable volume space, said means including a fixed part and a part movable with respect to said fixed part to vary the volume of said space, an auxiliary cylinder located in fixed position with respect to said fixed part, apassage connecting one end of said auxiliary cylinder with the said variable volume space, valve means in said passage arranged to be closed during the periods where said variable volume is in creasing an auxiliary piston reciprocable in said auxiliary cylinder, said auxiliary cylinder being divided by sad auxliary piston into two chambers, to wit a first chamber located at said above mentioned end of said auxiliary cylinder and a second chamber located at the other end of said auxiliary cylinder, a liquid delivery conduit leading from said' second spring means: interposed between" said auxiliary cylinder and said auxiliary piston for exerting on said auxiliary chambera check valve in said' delivery conduit. arranged to prevent'liquid fromflovving back -from fsaid delivery, conduit-to said second; chamber,

piston a return force opposed to that exerted on said auxft iliar y piston .by the liquid pressurefrom said variable volume space duringthe periods where said ,variable volume is decreasing, a by-pass conduit leading-from said first chamber'toisaid second chambegvalve means in said ,by-p'ass conduit operative to-close said by-pass point wheresaidiby-pass conduit opens into said second chamber being located inthewall "of said t-auxiliary cylinder ata'place such ,that' it isgclosed when both of said chambers are placed 'in1-communication with said ,discharge conduits," respectively. r e a 3 A pumpi according to claim 2 Vvvhich -the wall ofwsaid'auxiliary cylinder is provided with a groove in communication with the second discharge conduit, said groove extending, in'the; direction of the axis of said conduit dnring'a portion'of every; reciprocation of. said movable part, a first discharge conduit leadingto; the

outsidej from'a point ofthe cylindricaiwall'ot said auxr iliary cylinder, whereby said first chamber placed communication with said discharge :;conduit when said auxiliary piston has moved a given distance in said aux iliary cylinder away from said firstmentioned endthefreof, means in said discharge conduit for throttling thereof, a second discharge conduitmounted in fixed position 'with respect to said auxiliary cylinder, means-operative by said auxiliary piston to place said second'chamber in communication-with said second discharge; conduiLas soon as said first chamber'is placed in communication with said ;first discharge conduit, the point where-said by-pass conduit opens into said secondchamber being located inthe wall oi said auxiliary cylinder ataplace such that it is closed when both of said chambers are placed --in cornmnnicationwith said discharge conduits,

respectively.v a a 1 W 2. A'reciprocating action liquid pump which comprises, in combination, a main cylinder, a main piston reciprocable in said cylinder to form therewith a variable volume space, :an' auxiliary cylinder fixed with respect to said main cylinder, a passage connecting one end of'said auxiliary cylinder with the'end of said main cylinder where is located said variable volume space, an

, auxiliary piston reciprocable in said auxiliary cylinder, valve means in said passage arranged tobe closed dur-.

ing the strokesof said main piston which produce an increase of said variable lvolume space, said auxiliary j cylinder being divided bysaidauxiliary piston into two i chambers, to wit, a first chamber located at said' above mentionedend of said auxiliary cylinder andgasecond chamber located at the other end of {said auxiliary cylinder, a liquid delivery conduit leadingfrom said second I a chamber, a check valve insaid delivery conduit arranged to prevent liquid from flowing back from said delivery conduit to said. second chamber, spring means interposed between said auxiliary cylinder and said auxiliary piston for exerting on said auxiliary pis'ton a return force opposed to that exerted on said-auxiliary piston by the liquid pressure from said main cylinder duringthe delivery stroke of said main piston, a by-pass conduit leading fromsaid firstchamber to said second chamber, t valve means int'saidt by-pass conduit operativetto close said by-pass conduit during a portion'of every reciprocationof saidjmain piston, a first discharge conduit leading to the outside from a point of the cylindrical wall of said auxiliary cylinder, whereby said first chamber is placedin communication with said discharge conduit when said auxiliary piston has moved a given-distance in said auxiliary cylinder away from said first mentioned end thereof, means in said dischargeiconduit for throttling thereofia, second dischargeconduit mountedfiin auxiliary cylinder, from the openingof said second discharge conduit and in, the Qfirst mentioned direction of movement. of said auxiliary piston to adistance such that-said second discharge conduit remains in, communication with said second chamber for all positions. of said auxiliarypiston such that said first discharge conduit is in communication with said first chamber and said' second chamber is' out of. communication with said by-pass conduit;

' 4."A umpacoraingm1ain3 in which said means tor placing the second dischargev conduit in communication with the second chamberlco'nsists of a conduit ex- 'tending'through said auxiliary piston.- j o 5. A'pu'mp according to claim 2 furthercomprising means in said by passcOnduit 'for' throttlingfthereof." v

6;,A pump according to claimlin which said first discharge conduit comprises two branches said throttling means including athrottling member located in each of said branches, said two vthrottlingimembers' being arranged to have different throttling efiects respectively,

and'value means in said branches operative by pressure variations'insaid main cylinder to' open one of said branches ,2 and close the other when said auxiliary piston is moving'in one direction, and inversely. i c

. 7.,A pump according to' claim 2 further including a supplementary conduit extendingbetweensaid by-pass conduitand a point of the, second chamber located between the opening of'said by-pass'; conduit into said second chamber and said delivery conduit, with throttling means insaid supplementary conduit, I

'8LApump according to claim 2 in which said throttling means is automatically 'va'riable duringthe movementiof sfaid jauxiliary piston. in one direction.-

9 'A pump according to claim 6 in which at least one of, said throttling irnembersis automatically movable during'the movementof said auxiliary piston inone, direction] 4",, 1 i -t j a V 10. A pump according to -claim 2 further including a slide valve movably monntedacros's'said first discharge conduit to be able to 'controlithe' flow of liquid therethroughpresilientj means interposed between said discharge conduit and said slide-valve for urgingfsaid valve fixed position with respect to said auxiliary cylinder, i

meanswoperative by said auxiliary piston ctoj pla ce said second chamber in communication with saidvsecond 'discharge conduit as soon as'said firstc'hamber is placed in communication with said first discharge "conduit, the t,

ReferencesCited inthe file of this patent v UNITE D STATES PATENTS 2,281,045 Outin t- Apr. 28,1942 2,433,220 Huber Dec. 2 3, 1947 2,604,109 Tuttle July 22, 1952 2,725,890 Kanuch Dec. 5, 1955 V a FQREIGN PATENTS o -L 1 402,603 Great Britain. Dec; 7, 1933 I 760,600 France Dec. 14, 1933 

